argparse

CLI arguments parser for node.js, with sub-commands support. Port of python's argparse (version 3.14.6).

Difference with original.

• JS has no keyword arguments support.
  • Pass options instead: new ArgumentParser({ description: 'example', add_help: true }).
• JS has no python's types int, float, ...
  • Use string-typed names: .add_argument('-b', { type: 'int', help: 'help' }).
• %r format specifier uses require('util').inspect().

See the complete list of differences from Python. Users upgrading from v2 should read the migration guide.

Example

Following code is a JS program that takes a list of integers and produces either the sum or the max:

const { ArgumentParser } = require('argparse')

const parser = new ArgumentParser({ description: 'Process some integers.' })

let sum = ints => ints.reduce((a, b) => a + b)
let max = ints => ints.reduce((a, b) => a > b ? a : b)

parser.add_argument('integers', { metavar: 'N', type: 'int', nargs: '+',
                                  help: 'an integer for the accumulator' })
parser.add_argument('--sum',    { dest: 'accumulate', action: 'store_const',
                                  const: sum, default: max,
                                  help: 'sum the integers (default: find the max)' });

let args = parser.parse_args()
console.log(args.accumulate(args.integers))

Assuming the JS code above is saved into a file called prog.js, it can be run at the command line and provides useful help messages:

$ node prog.js -h
usage: prog.js [-h] [--sum] N [N ...]

Process some integers.

positional arguments:
  N           an integer for the accumulator

options:
  -h, --help  show this help message and exit
  --sum       sum the integers (default: find the max)

When run with the appropriate arguments, it prints either the sum or the max of the command-line integers:

$ node prog.js 1 2 3 4
4
$ node prog.js 1 2 3 4 --sum
10

If invalid arguments are passed in, it will issue an error:

$ node prog.js a b c
usage: prog.js [-h] [--sum] N [N ...]
prog.js: error: argument N: invalid 'int' value: 'a'

This is an example ported from Python. You can find detailed explanation here.

API docs

Since this is a port with minimal divergence, there's no separate documentation. Use original one instead, with notes about difference.

1. Original doc.
2. Original tutorial.
3. Differences from Python.
4. Migration from v2 to v3.